The Mars rover Opportunity has discovered what scientists say is the first meteorite of any type ever identified on another planet.
Opportunity encountered the basketball-sized hunk of iron and nickel during a study of its landing site in the Meridiani Planum region and used its onboard instruments to confirm the meteorite's origins, principal scientist Steve Squyres said Wednesday.
"We have been driving around on the plain seeing lots of little rocks the size of a fist or a potato -- we call them cobbles," Squyres said. "Now we're not so sure they're just lumps of rock. Suppose they are meteorites?"
If the cobbles are meteorites, scientists would then begin probing whether martian winds are depositing sand on the planet's surface or scouring the surface to reveal rocks.
"Most of what we see is evidence that this area has undergone a lot of stripping. You don't have to go down in this [sand] very far before you hit rock," Squyres said.
The martian sands may be similar to an Earth process in which melting ice reveals fields of meteorites in Antarctica, Squyres said.
The frozen plains there have yielded concentrations of meteorites that fell to Earth over the last million years and were deposited together by ice flows.
The pitted martian meteorite, nicknamed Heat Shield Rock, lies a few yards from where Opportunity's heat shield came to rest when the rover landed on Jan. 24, 2004.